1. Field of the Invention
The present invention relates to a moisture proof hinge. More specifically, the invention relates to a moisture proof hinge for use as part of a flexible boundary in a fluid passageway.
2. Description of the Related Art
Hinges are used in a multitude of settings to provide an articulable connection between two structures. Typically, hinges are used to connect components so that the angle between the two components can be changed while maintaining a structural connection. In some applications, articulable connections are needed in fluid systems, for example, particularly as a part of a fluid passage.
Articulable connections have long been required for feed boxes for static sieves, sieve bends or screens of the type shown in FIG. 5. Articulable connections 10 are used to control the flow of fluid from the feed box 40 onto the sieve 45. See for example, the Static Sieve Feed Control of Connolly, U.S. Pat. No. 4,710,296.
In such an assembly, the feed box 40 is a relatively large hollow container for holding a fluid, generally a slurry of solid particles and water. The feed box is filled through an inlet opening 41 and the feed box is emptied, generally, by the force of gravity through an opening 42 in the bottom of the feed box 40. Typical feed boxes are rectangular in shape, much longer than they are deep or wide. A feed box of this shape is suited for distributing the slurry over a wide area through the long slot defined at the bottom of the feed box.
Depending upon the consistency of the slurry to be fed to the sieve, the flow rate of the slurry from the box to the sieve must be controlled. For example, a viscus slurry is often fed at a slower rate than a non-viscus slurry depending upon the performance of the sieve 45. Thus, it is necessary to control the flow of slurry from the feed box.
A conventional control apparatus is disclosed in the aforementioned Connolly patent. That control apparatus, also illustrated in FIG. 5 consists of a discharge spout 43 having a rigid back 44 wall, rigid side walls (not shown), and a control wall having two portions. The upper control wall 46 is rigid and extends downward from the top of the discharge spout which connects with the bottom of the feed box. A lower control wall 47 extends the upper control wall 46 towards the bottom of the discharge spout. The upper control wall 46 and the lower control wall 47 are connected by an articulable connector 10 so that the lower control wall can be angled toward the back to eventually contact the back wall thus closing the discharge spout. The lower control wall is pivoted about the articulable connection by the force of a handle and cam mechanism 48 connected to a discharge spout frame, or by a threaded limit bolt (not shown), which, when turned, presses against the surface of the lower control wall.
The articulable connection in early feed boxes was a conventional straight hinge that extended along the length of the discharge spout and was connected to the upper and lower control wall. However, such connections had the disadvantage that they leaked because slurry would penetrate the joint of the hinge and pass through it to escape the discharge spout. This leakage was more pronounced when the lower control wall portion 47 was displaced to stop the flow from the feed box. In this condition there is substantial pressure forcing fluid through the hinge when the feed box is full.
To address this problem, other articulable connections have been used, as in the Connolly structure. Connolly provided a strip of rubber material, for example polyurethane or like elastomeric flexible material, which extends along the lower edge of the upper control wall and is connected to the upper control wall at spaced locations. A lower edge of the rubber strip is connected to the upper edge of the lower control wall such that the lower control wall is suspended from the wall, not by a hinge, but by the flexible piece of rubber. The continuous piece of rubber seals the gap between the upper and lower control wall and allows the lower control wall to be articulated relative to the upper wall.
However, a deficiency of this connection is that the rubber seal is the only structural connection between the upper and lower control walls and the rubber or other resin material may not have sufficient durability and strength to provide a long term, reliable connector. When the feed box is full of slurry or other fluid and the control wall is closed, there is significant stress on the connector which supports much of the load on the lower control wall. That stress and the repeated flexure of the hinge over time can cause the elastomeric hinge to break down quickly, leading to leaks and eventual failure of the connection, thus requiring time consuming and expensive replacement of the connection.